When backing up a system, what type of files should be archived, and what types should not?

What will be an ideal response?

A typical Linux system can include hundreds of thousands of files, but you don't have to include all of them in an archive. For example, you don't have to include temporary files in the /tmp and /var/tmp directories, nor do you need to include any cached Internet content found in the .mozilla directory (if you use the Mozilla Firefox Web browser) under each user's home directory.?As a rule of thumb, you should back up user files from home directories and any important system configuration files such as /etc/passwd. In addition to this, you might want to back up files used by system services. For example, you need to back up Web site files if the Linux computer is used as a Web server. Programs such asgrep and vi need not be backed up because they can be restored from the original installation media in the event of a system failure.